The present invention relates generally to a cleaning apparatus and in particular relates to a parts washing apparatus for cleaning metal parts, such as is commonly employed in garages, machine shops, factories, etc.
In the past, it was common to clean oily and greasy metal parts, such as automobile parts and machined metal parts in a machine shop, using simply a bucket containing a quantity of gasoline and a stiff brush. Gasoline is very effective as a solvent in dissolving greases and oils into the gasoline. However, certain problems existed with this approach. Firstly, gasoline is highly flammable, presenting a substantial danger of fire and explosion. Secondly, prolonged skin contact with gasoline can lead to irritation and other health problems. Thirdly, gasoline vapors are harmful when inhaled. Fourthly, the solvent-in-a-bucket approach leads to fairly rapid contamination of the solvent.
Many of these shortcomings of the solvent-in-a-bucket approach were largely overcome by the introduction of the solvent-based sink washers which have proliferated in recent years. The Safety Kleen Corporation of Elgin, Ill. has placed and serviced untold numbers of parts washers generally made in accordance with U.S. Pat. No. 3,522,814. As taught in the ""814 patent, solvent (nominally mineral spirits) is re-circulated through a tank and a sink, and a removable liner or bag is provided which can be easily removed and discarded to remove contaminants from the solvent (at least some of the contaminants). The sink includes a hinged cover which is held in place by a fusible link such that in the event of fire, the fusible link melts and allows the cover to close over the sink, thereby reducing the risk of further fire and/or explosion. The solvent sink described in the ""814 patent and distributed and serviced by Safety Kleen Corporation has been almost universally embraced by garages, factories, repair shops of all types, machine shops, etc.
Despite this wide-spread success of the solvent-sink type parts washer, some problems remain with the use of solvents in the washing of parts. For example, while such solvents are less prone to ignition than is gasoline, they still present something of a risk of fire. Moreover, such solvents inherently have environmental problems associated with them. Such environmental problems are attendant upon the production, distribution, use, and reclamation of such solvents. Moreover, such solvents can present an occupational safety hazard, both in terms of breathing noxious vapors and irritation (and perhaps other problems) associated with direct contact with the user""s skin.
While the solvent-based parts washers are still in extremely widespread use and are still very effective for cleaning parts, many people have recognized that there is a need for a non-solvent based system. Thus, numerous attempts have been made to provide an aqueous-based parts washer. In general, these have suffered from problems as well, most notably a lack of effectiveness. In addition, prior aqueous-based parts washers have tended to be large and bulky, expensive, involve the use of caustic solutions, and the solutions employed have become quickly contaminated.
For example, one type of parts washer that has been used in the past is the so-called automatic jet washer. Such a machine is, in concept, similar to a kitchen dishwasher. The parts are placed in a cabinet and the cabinet is sealed up. Then a water-based detergent solution is sprayed onto the parts in a narrow, high impact spray pattern and either the parts are rotated through the spray pattern or the spray pattern is rotated around the parts. Normally, the water-based detergent solution is heated to improve the cleaning abilities of the solution. Such automatic jet washers are normally expensive and bulky. Moreover, because of the closed cabinet, they normally do not allow hand cleaning of parts, which can be a drawback when one wants to do just a little more cleaning of a part that has already been cleaned or one wants to clean only lightly a part which has not yet been cleaned.
As described in the background portion of U.S. Pat. No. 5,650,385, it has also been known to provide a sink-type parts washer using an aqueous solution. However, as described in the ""385 patent, known solutions used in such sink-type parts washers have tended to be exceedingly alkaline, having pH values of 13 and above in order to provide effective cleaning of the parts. However, solutions with such high pH""s tend to be highly corrosive both to the parts and to the users of the cleaning apparatus. The ""385 patent further describes that the use of a more moderate pH aqueous solutions tends to compromise the effectiveness of the solution, thereby reducing its desirability.
In addition to the effectiveness problem identified above and the pH (corrosiveness) problem identified above, another problem exists with the use of aqueous-based solutions. Once an aqueous based solution is used effectively to clean metal parts, such an aqueous-based solution typically becomes contaminated rather quickly. In the known prior art, it has been common to use highly detergent solutions which have the effect of completely emulsifying oils and greases in the solution. Once the solution becomes heavily laden with emulsified greases and oils, the effectiveness of the solution for further cleaning subsequent parts is dramatically reduced. Moreover, even where the effectiveness of the solution can be maintained, it often gives the appearance of being xe2x80x9cdirtyxe2x80x9d, thereby reducing user confidence therein.
Accordingly, it can be seen that a need yet remains for a parts washing apparatus which utilizes an aqueous based solution and which is effective, safe, and economical. Moreover, it can be seen that a need yet remains for such an apparatus in which the effectiveness of the solution and the cleanliness thereof can be maintained over many uses thereof. It is to the provision of such a parts washer apparatus that the present invention is primarily directed.
Briefly described, in a preferred form, the present invention comprises an ultrasonic cleaning apparatus for use with a cleaning solution for cleaning items, such as automobile parts. The apparatus includes a cleaning tank for containing a quantity of the cleaning solution therein in which items to be cleaned can be placed therein. The apparatus includes an ultrasonic generator for ultrasonically exciting the cleaning solution contained within the cleaning tank. At least one upper drain is provided for drawing liquid from adjacent an upper surface of the cleaning solution contained within the tank. The apparatus also includes at least one lower drain for drawing liquid from adjacent the bottom of the cleaning tank. In one embodiment, control means are provided to draw liquid at times from the upper drain and for at other times drawing liquid from the lower drain. Also, a filter is provided for filtering liquid drawn from the cleaning tank and returning filtered liquid to the cleaning tank. Also preferably, the filter comprises a coalescing filter.
Preferably, the control means is operable for alternately drawing liquid from the lower drain and from the upper drain in an alternating cycle. Preferably, the alternating cycle of drawing from the upper drain and then from the lower drain is utilized when the ultrasonic generator is not operating. Alternatively, the control means is adapted for continuously drawing liquid from the upper drain. Also preferably, a pump is provided for recirculating cleaning solution through the filter and the tank.
Further, the invention preferably includes a sump tank, which does not have to be a separate tank, for housing an additional quantity of cleaning solution which, at times, can be pumped into the cleaning tank to facilitate the removal of light ends of oils and greases from the cleaning tank by raising the level of cleaning solution in the cleaning tank.
In another aspect, the present invention relates to an ultrasonic parts cleaning apparatus for cleaning items comprising a tank for containing a quantity of a cleaning solution, the cleaning tank having a bottom; a filter for filtering the cleaning solution; a pump for continuously recirculating cleaning solution through the tank and the filter; a sump associated with the tank and pump for continuously adding additional cleaning solution to the tank to facilitate the drawing off of light ends of greases and oils from the solution; an ultrasonic device for ultrasonically exciting cleaning solution within the tank; and a control means operable for controlling the pump in a continuous cleaning cycle wherein the cleaning solution is continuously pumped through the filter and returned to the tank.
In another preferred form, the present invention comprises a method for cleaning items, such as automobile parts, using an ultrasonic cleaning apparatus and a cleaning solution. The ultrasonic cleaning apparatus includes a tank for containing a quantity of the cleaning solution and a filter for filtering the cleaning solution. The ultrasonic cleaning apparatus further includes a pump for recirculating the cleaning solution through the tank and through the filter. An ultrasonic device is used to excite the cleaning solution within the tank. The method includes the steps of operating the apparatus in a parts cleaning cycle at times and at other times operating the apparatus in a solution cleansing cycle. In the parts cleaning cycle, the parts are placed in the tank to be cleaned, the ultrasonic device is operated, and the parts are removed from the tank. In the solution cleansing cycle, the cleaning solution is pumped through a filter and returned to the tank. In the solution cleansing cycle, at times the cleaning solution is drawn from the top of the tank for pumping through the filter and at other times the cleaning solution is drawn from the bottom of the tank for pumping through the filter. In this way, light ends of the oils and greases can be removed from the top of the cleaning solution, and heavy ends of greases and oils can be removed from the bottom of the cleaning solution.
In another aspect, the method of the present invention involves a method for cleaning items using an ultrasonic cleaning apparatus and a cleaning solution, with the ultrasonic cleaning apparatus including a tank for containing a quantity of the cleaning solution, a filter for filtering the cleaning solution, a pump for continuously recirculating the cleaning solution through the tank and the filter, a sump associated with the tank and pump for continuously adding additional cleaning solution to the tank and an ultrasonic device for ultrasonically exciting the cleaning solution within the tank, the method comprising the steps of: (i) placing parts to be cleaned into the tank; (ii) operating the ultrasonic device; (iii) continuously drawing cleaning solution from the tank to the sump for pumping through the filter; (iv) continuously pumping the cleaning solution from the sump through the filter and returning the filtered cleaning solution to the tank; and (v) removing the parts from the tank.
The apparatus according to the present invention has proven to be extremely effective in cleaning soiled parts. Also, the solution is maintained in a clear, clean condition for a relatively long time, even after repeated uses. The apparatus advantageously avoids the use of solvents, instead using a water-based cleaning solution. Moreover, the water-based (aqueous) solution is mild by comparison to known prior art aqueous solutions, which tended to be rather caustic.
Such a method and apparatus is simple, durable, and easily used. It is also environmentally friendly in that no solvents need be used or reclaimed in the use of the equipment. Moreover, the use of mild aqueous-based solution is inherently safer than the use of solvents. Also, the use of such a mild aqueous solution is less harmful to the human operators thereof, both in terms of any vapors that might be inhaled and contact with someone""s skin.
Accordingly, it is a primary object of the present invention to provide a parts cleaning apparatus using an aqueous cleaning solution, which is highly effective for cleaning parts.
It is another object of the present invention to provide a parts cleaning apparatus for use with an aqueous cleaning solution, which is effective for maintaining the usefulness of the cleaning solution over many uses thereof.
It is another object of the present invention to provide a parts cleaning apparatus and method utilizing an aqueous cleaning solution, which apparatus and method is effective for efficiently separating the cleaning solution from oils and greases.
It is another object of the present invention to provide a parts cleaning apparatus and method which is simple in its construction, durable in operation and easily operated and maintained.